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United States Patent |
6,202,832
|
Evansic
|
March 20, 2001
|
Spring connection mechanism for vibratory feeders
Abstract
A vibratory conveying apparatus includes a trough operatively associated
with a vibratory drive assembly for conveying pieces along the trough. The
vibratory drive assembly includes a base member and a vibratory drive
mounted to the base member. The trough is operatively associated with the
vibratory drive to be driven into vibration substantially longitudinally
with respect to the base member. First and second flexure members or bars
extend longitudinally of the base member on opposite lateral sides of the
base member, the bars connected at base ends to the base member. At least
one leaf spring extends laterally across the base member, the leaf spring
connected at opposite ends to distal ends of the bars and operatively
connected at a center thereof to the trough. The flexure members provide
increased flexibility at the leaf spring connections to increase useful
spring life.
Inventors:
|
Evansic; Leonard (Graceton, PA)
|
Assignee:
|
FMC Corporation (Chicago, IL)
|
Appl. No.:
|
320053 |
Filed:
|
May 26, 1999 |
Current U.S. Class: |
198/769 |
Intern'l Class: |
B65G 027/24 |
Field of Search: |
198/769
|
References Cited
U.S. Patent Documents
1601247 | Sep., 1926 | Garbarini.
| |
2098034 | Nov., 1937 | Flint et al. | 198/56.
|
2481131 | Sep., 1949 | Lindsay | 198/220.
|
3404299 | Oct., 1968 | MacBlane | 310/17.
|
3845857 | Nov., 1974 | Doty.
| |
4121708 | Oct., 1978 | Benson et al. | 198/766.
|
4813532 | Mar., 1989 | Harper | 198/760.
|
4880106 | Nov., 1989 | Falconer et al. | 198/763.
|
5285890 | Feb., 1994 | Stearns | 198/766.
|
5287027 | Feb., 1994 | Marshall et al. | 310/21.
|
5664664 | Sep., 1997 | Gaines | 198/769.
|
5757092 | May., 1998 | Graham | 310/15.
|
5821657 | Oct., 1998 | Falconer et al. | 310/91.
|
5865297 | Feb., 1999 | Chiba et al. | 198/751.
|
5931286 | Aug., 1999 | Illi | 198/769.
|
5967294 | Oct., 1999 | Patterson et al. | 198/763.
|
6019216 | Feb., 2000 | Patterson | 198/752.
|
6041915 | Mar., 2000 | Fishman et al. | 198/766.
|
6079549 | Jun., 2000 | Meitinger | 198/751.
|
6079550 | Jun., 2000 | Gilman | 198/769.
|
Primary Examiner: Bidwell; James R.
Attorney, Agent or Firm: Rockey, Milnamow & Katz, Ltd.
Claims
The invention claimed is:
1. A vibratory conveying apparatus, comprising:
a base member;
a vibratory drive mounted to said base member;
a trough operatively associated with said vibratory drive to be driven into
vibration longitudinally with respect to said base member,
first and second bars each extending longitudinally between base and distal
ends, of said base member on opposite lateral sides of said base member,
said bars connected at said base ends to said base member; and
at least one leaf spring extending laterally across said base member, said
leaf spring connected at opposite ends of said leaf spring to said distal
ends of said bars and operatively connected at a center thereof to said
trough each of said bars having a lateral flexibility between said base
end and said distal end thereof.
2. The apparatus according to claim 1, wherein said bars each include a
clamping element at said distal ends, said leaf spring being clamped to
said bars at said clamping element.
3. The apparatus according to claim 1 comprising a plurality of leaf
springs and a plurality of spacers, adjacent ones of said leaf springs
separated at said opposite ends by said spacers.
4. The apparatus according to claim 1, wherein said bars each include a
clamping element at said distal ends, and said leaf spring is clamped to
said bars at said clamping element, wherein said clamping elements each
comprise a block-shaped element extending parallel to said respective bar
and having a base end connected to said distal end of said bar and a
distal end extending toward said base end of said bar, said clamping
element and said bar having openings therethrough that are in registry for
receiving said leaf spring, and said block-shaped element having a
threaded opening in said base end thereof which extends into said opening
for receiving a fastener which abuts said leaf spring to clamp said leaf
spring against said block-shaped element.
5. The apparatus according to claim 4, comprising a trough chassis
connected to said trough and which includes a lateral opening therethrough
for allowing said leaf spring to penetrate through said chassis, and a
threaded opening through an end face of said chassis, said threaded
opening open into said lateral opening for receiving a threaded fastener
therein for clamping said leaf spring to said trough chassis.
6. The apparatus according to claim 1, wherein said vibratory drive
includes an electromagnet mounted to said base member and an armature
mounted to said trough in close proximity to said electromagnet.
7. The apparatus according to claim 1, comprising two block-shaped clamping
elements, one of which is fixed to a distal end of each of said bars, each
bar and clamping element pair having windows therethrough in registry,
said leaf spring received into said windows of said bars and said clamping
elements, and including two clamping fasteners, each fastener protruding
through a front wall portion of one block-shaped clamping element to
pressingly capture said leaf spring against a wall of said window of said
clamping element.
8. A vibratory conveying apparatus, comprising:
a base member;
a vibratory exciter supported on said base member;
a vibratory output member that is vibrated with respect to said base member
by said vibratory exciter;
a first bar extending longitudinally of said base member between a base end
and a distal end thereof and connected at said base end thereof to said
base member;
a second bar extending longitudinally of said base member between a base
end and a distal end thereof and connected at said base end thereof to
said base member;
a leaf spring arranged across said base member and connected to distal ends
of said first and second bars, each of said bars having a lateral
flexibility between said base end and said distal end thereof; and
said output member connected to a central area of said leaf spring.
9. The apparatus according to claim 8 further comprising a trough connected
to said output member.
10. The apparatus according to claim 8, comprising a plurality of
additional leaf springs arranged across said base member and connected to
distal ends of said first and second bars, and a plurality of spacers, and
adjacent ones of said plurality of additional leaf springs are separated
by spacers, said output member connected to a central area of said
plurality of additional leaf springs.
11. The apparatus according to claim 8, wherein said bars and said output
member include spring openings in registry for accepting said leaf spring
laterally across said base member, and three clamp mechanisms for clamping
the leaf spring at opposite ends to said bars and at a central region to
said output member.
12. The apparatus according to claim 11, wherein said three clamp
mechanisms each include a structure adjacent to each of said spring
openings, each of said structures having a threaded aperture open into a
respective spring opening, and a threaded fastener threaded into said
threaded aperture, and protruding into said respective spring opening.
13. A vibratory conveying apparatus, comprising:
a base member;
a trough elongated longitudinally;
at least one elongated flexure member having a base end and a distal end;
and
at least one leaf spring having a first end and a second end, and extending
at an angle to said elongated flexure member and connected at said first
end thereof to said distal end of said elongated flexure member, said
flexure member and said leaf spring connected in series between said base
member and said trough at said base end and said second end.
14. The conveying apparatus according to claim 13, wherein said flexure
member base end is connected to said base member, and said leaf spring
second end is connected to said trough.
15. The conveying apparatus according to claim 13, comprising a plurality
of leaf springs, wherein said leaf spring is one member of said plurality
of leaf springs, said plurality of leaf springs stacked to form a bank of
leaf springs.
16. The conveying apparatus according to claim 15, wherein said flexure
member is connected to said base member by fasteners at said base end
thereof, at the distal end of said flexure member includes a clamping
element for clamping said first ends of said plurality of leaf springs.
Description
TECHNICAL FIELD OF THE INVENTION
The invention relates to a vibratory feeder or conveyor that employs leaf
springs. Particularly, the invention relates to an improved leaf spring
connection for a vibratory feeder or conveyor, the feeder or conveyor
having a base member and relatively reciprocating trough connected to the
base member by the leaf springs.
BACKGROUND OF THE INVENTION
Vibratory feeders and conveyors are known which employ bar shaped leaf
springs connecting a trough to a base member. The leaf springs in these
feeders or conveyors may be mounted individually, or in banks of multiple
leaf springs to meet the spring rate required by the design of the
vibratory equipment. The leaf springs are known to be arranged such that
one end of the bank of leaf springs is clamped to the conveying member,
for example, the trough of the vibratory feeder, and the other end is
clamped to the base member, or to the stationary member in the case of a
single mass feeder design. In some designs, a center region of the bank of
springs is clamped to structure of the conveying member of the feeder or
conveyor, while the ends of the bank of leaf springs are clamped to
structure of the base member, forming two spring bank sections.
A problem associated with these prior art designs is that as the spring
bank is deflected, the leaf springs are required to elongate due to the
geometry of the spring bank configuration. This elongation subjects the
leaf springs to very high tensile stress as the leaf springs try to
stretch. Also, as the feeder operates in each vibration cycle, the leaf
springs are required to first deflect, in a characteristic "S" shaped
form, in one direction, then to return to pass through a neutral position,
and then to deflect in the opposite direction, and then to return to the
neutral position once again to complete the cycle. Thus, with each cycle,
the leaf springs experience a fully reversing stress which is detrimental
to the useful life of the leaf springs.
The generated forces acting along a spring axis are directed to urge the
leaf springs in the spring bank to slip in their clamped connection during
some stage of deflection. If the clamping force at the clamped connection
is increased to prevent such slippage at this stage of deflection, the
resulting tensile stress, combined with the increased bending stress of
the spring, particularly at the stress riser location formed where the
spring is clamped, is often sufficient to cause a premature failure of a
leaf spring as it is deflected back and forth.
There have been some prior art attempts to alleviate the design problem
discussed in the previous paragraph, by fixing one end of the leaf
springs, say to the base member of the conveyor or feeder, and allowing
the other end of the spring to rotate. U.S. Pat. No. 3,845,857 discloses
an arrangement of a single mass vibratory feeder wherein one end of a
spring bank is connected to a rod mounted in an elastomer bushing such
that as the spring element are deflected, the bushing yields, allowing the
spring ends to move to provide a substantially simple deflection of the
spring. This connection avoids the "S" shape form characteristic of
deflecting a leaf spring that is fixed at both ends. While this spring
mounting means may reduce the spring stresses involved in the deflection,
the resultant spring rate would be reduced to an extent that would make
the system impractical for large feeders.
SUMMARY OF THE INVENTION
The present invention contemplates a vibratory conveying apparatus, such as
a conveyor or feeder, having a vibratory drive assembly and a trough. The
trough is connected to a base member of the vibratory drive assembly via a
leaf spring assembly. The leaf spring assembly has an improved spring
connection configuration located between the trough and the base member to
decrease stress on a leaf spring or springs of the leaf spring assembly to
increase the useful life of the leaf spring assembly, while still
providing an effective spring rate.
The apparatus includes a vibratory drive arranged between the base member
and the trough. The vibratory drive can be an electromagnetic driver, a
rotating eccentric weight driver, a rotating crank arm driver, or other
type of drive which acts directly on the trough, or acts to indirectly
induce vibration through the spring assembly, such as in a base excited
conveyor.
The leaf spring assembly preferably includes a plurality of leaf springs
stacked together in a spring bank, although a leaf spring assembly having
a single leaf spring is also encompassed by the invention. Where a
plurality of leaf springs are employed, the springs can be separated by
spacers.
In a preferred embodiment, the leaf springs are arranged in a bank and
extend substantially perpendicularly to a first direction of vibratory
movement of the trough. The leaf springs are connected at a first region
to a flexure member and at a second region to structure of the trough. The
flexure member is elongated in the first direction, having a base end
fastened to the base member and a distal end connected to the leaf
springs. The flexure member can flex laterally at its distal end in
response to flexing force from the leaf springs.
Preferably, the first region is one end of the leaf springs and the second
region is a center region of double length leaf springs. The leaf springs
can also include a third region at an opposite end of the double length
leaf springs. A second flexure member is connected at its base end to the
base member and at its distal end to the third region. The first and
second flexure members are configured and arranged in mirror image fashion
on opposite lateral sides of the base member.
Each flexure member includes a substantially plate shaped bar member
extending substantially along its length from the base end to the distal
end. The flexure member includes a clamp element or clamp block connected
to the distal end of the bar member. The bar member and the clamp element
include openings in registry for accepting one or more leaf spring
elements. A fastener proceeds into the distal end of the clamp element to
be advanced along the first direction to abut the leaf spring(s) and press
the leaf spring(s) against an end surface of the opening to clamp the
spring(s) into the clamp element.
The spring attachment mechanism of the present invention is an improvement
over the prior known arrangement in that it lowers the spring stresses
while maintaining high spring rates for practical designs of large two
mass vibratory feeders and conveyors. According to the preferred
embodiments of the invention, the characteristic "S" shape form of the
deflected leaf spring is retained.
The invention provides an improved means to mount and connect leaf springs
used in vibratory feeders and conveyors such that combined tension and
bending stresses are minimized. These lower stresses prevent premature
spring failure which allows higher vibration strokes than feeders and
conveyors using conventional spring clamping methods. The attachment
mechanism accommodates a high system spring rate to keep the number and
the size of the springs within practical limits.
Numerous other advantages and features of the present invention will become
readily apparent from the following detailed description of the invention
and the embodiments thereof, from the claims and from the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a vibratory conveying apparatus utilizing a
vibratory drive assembly of the present invention;
FIG. 2 is an enlarged elevational view of the vibratory drive assembly
shown in FIG. 1;
FIG. 3 is an elevational view of the drive assembly of FIG. 2;
FIG. 4A is a plan view of a base member of the assembly of FIG. 2;
FIG. 4B is an elevational view of the base member of FIG. 4A;
FIG. 4C is an end view of the base member of FIG. 4A;
FIG. 5A is a plan view of vibratory components of the assembly of FIG. 2;
FIG. 5B is an elevational view of the vibratory components of FIG. 5A;
FIG. 6A is a plan view of a flexure member of the assembly of FIG. 2;
FIG. 6B is an elevational view of the flexure member of FIG. 6A;
FIG. 7 is a schematic plan view of the assembly of FIG. 2; and
FIG. 8 is a schematic view of an alternate embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While this invention is susceptible of embodiment in many different forms,
there are shown in the drawing and will be described herein in detail
specific embodiments thereof with the understanding that the present
disclosure is to be considered as an exemplification of the principles of
the invention and is not intended to limit the invention to the specific
embodiments illustrated.
FIG. 1 illustrates a conveying apparatus 10 of the present invention. The
apparatus 10 can be a vibratory conveyor or feeder. The apparatus includes
a trough 20 for holding pieces to be conveyed in the direction X. A
vibratory drive assembly 14 (described below) is connected to the trough
20 and can be hung via one or more rods 13 from a support structure 17,
for example, in the case of a single mass feeder or conveyor. The trough
20 can also be supported from the support structure 17 via one or more
rods 13a. Power is supplied to a vibratory drive 34 (described below)
located within the drive assembly 14, via an electric power cord 44, to
drive the trough into vibration along the axis A.
The trough 20 is connected to the drive assembly 14 by means of one or more
trough brackets 21 connected by fasteners 19 to one or more connector
brackets 22 (shown in FIG. 2). The connector brackets 22 are connected to
the vibratory drive assembly 14.
FIG. 2 illustrates the vibratory drive assembly 14. The assembly includes a
base member in the form of a base assembly 16. The base assembly 16 is
supported from the structure 17 by the rod(s) 13, as shown in FIG. 1. The
connector brackets 22 are connected to a trough frame or chassis 24 via
four extending arms 24a (two shown in FIG. 2). The trough chassis 24 is
supported by a bank 25 of leaf springs 26.
The electric power cord 44 is passed through a rubber strain relief bushing
33, fastened to the base assembly 16, to protect the cord from pulling
loose or fraying.
The base assembly 16 is described below with respect to FIGS. 4A through
4C. The base assembly 16 forms a substantially enclosed space for the
chassis 24 and the vibratory drive 34. The enclosure is formed by a cover
plate 92, a top plate 100, a base plate 108, a back plate 102 and two
flexure members 54 (described below). The connector brackets 22 are each
welded or otherwise connected to two of the four extending arms 24a of the
chassis. The brackets 22 each include six threaded holes 120 for receiving
the fasteners 19, to connect each of the trough brackets 21 to one of the
connector brackets 22.
FIG. 3 illustrates the vibratory drive assembly 14. The cover plate 92 and
the top plate 100 are removed for clarity of description. The vibratory
drive 34 is mounted to the base assembly 16 and operates to impart
vibration between the base assembly 16 and the trough 20. The vibratory
drive 34 includes an electromagnet 38 having an electromagnetic coil 48.
The trough chassis 24 includes an armature 40 in close proximity to the
electromagnetic coil 48 such that an oscillating magnetic field in the
coil 48 causes the armature 40 to be repetitively drawn toward and then
released from the coil 48. The electric power cord 44 conducts electric
power to the coil 48. The electromagnet 38 is mounted to the base assembly
16 via a mounting bracket 50 and fasteners 52.
The leaf springs 26 are connected at opposite ends to respective flexure
members 54. Each flexure member 54 includes an elongated bar element 56
having a base end 57 and a distal end 59. The base end 57 of the bar
element 56 is fastened by fasteners 69 to respective side members 106
(described below) of the base assembly 16. Connected at the distal end 59
is a block-shaped clamp element 60. The bar element 56 includes a bar
window or opening 58 adjacent to its distal end 59. The clamp element 60
extends in a direction from the distal end 59 of the bar element 56 back
toward the base end 57 of the bar element 56. The clamp element 60
includes a clamp window or opening 62 which is in registry with the bar
window 58 of the bar element 56.
A clamp fastener 64 extends through a front wall portion 66 of the clamp
element 60, threaded into a threaded bore 71. The clamp fastener 64
extends into the window 62 when the clamp fastener 64 is advanced in the
element 60. The fastener 64 has a protrusion 64a that presses against a
clamp block 63 which presses against the plurality of springs 26. The
springs 26 can be spaced apart by interleaved spacers 65. The bank of
springs 25 is clamped tightly within the window 62 against a stop block 67
which is pressed to an end surface 68 of the clamp window 62. The bank of
springs 25 passes loosely through the bar window 58.
The chassis 24 includes a transverse slot or opening 80. The springs 26
extend through the opening 80. A stop block 67, a clamp block 63 and
spacers 65 between adjacent springs 26, are arranged within the opening
80. A further clamp fastener 64 extends through a front wall portion 86 of
the chassis 24. Advancement of the further clamp fastener 64 through the
front wall portion 86 presses the clamp block 63 into the bank of springs
25 against the clamp block 67 which itself abuts an end surface 84 of the
chassis 24. Thus, the springs are tightly clamped at each of the flexure
members 54 and at a center region thereof within the chassis 24.
FIGS. 4A and 4B illustrate the base assembly 16 of the apparatus. The base
assembly includes the top plate 100 supported from the base plate 108 by
the back plate member 102, the two side members 106 and two front support
members 116. The top plate 100 includes an access opening 101 above the
vibratory drive 34, for maintenance access. The access opening 101 is
closed by the cover plate 92, as shown in FIG. 2. The side members 106
include threaded holes 107 for receiving the fasteners 69, as shown in
FIG. 2. Extending upwardly from the base plate 108 are two electromagnet
support blocks 112, which support the mounting bracket 50, each of which
contain bracket mounting holes 126 which are threaded to receive the
fasteners 52.
FIGS. 5A and 5B illustrate the vibratory driver 34 arranged adjacent to the
armature 40. The electromagnet mounting plate 50 includes four fasteners
holes 126 which are elongated longitudinally in order to precisely set the
distance of the electromagnetic coil 48 to the armature 40.
FIGS. 6A and 6B illustrate the flexure member 54 in more detail including
the rectangular clamp window 62 which is open to the threaded bore 71. The
flexure member mounting holes 130 are used to receive the fasteners 69.
FIG. 7 illustrates the vibrational behavior of the trough chassis 24, the
spring bank 25 and the flexure members 54 during operation of the
apparatus. Although only one double length spring 26 is shown for
simplicity, the behavior of all of the leaf springs 26 of the bank 25
would be similar. As the apparatus operates, in each vibration cycle each
of the springs 26 first deflects from a neutral position to its
characteristic "S" shaped form, in one direction, returns to pass through
the same neutral position, and then deflects in the opposite direction,
and then returns to the neutral position to complete the cycle. As the
spring bank 25 is deflected, the tension, due to the spring elements
trying to elongate, and the axial bending strain, produce a force whereby
the elongated bar element 56 of the flexure member 54 deflects along its
own "S" shaped path in the direction defined by the arrows 144. The
selected spring rate of the flexure member 54 limits the combined stress
level in the spring system 26 to be within safe design values for long
spring life, but at the same time is sufficiently stiff to provide a
resultant spring rate to handle the trough weights of the largest of
vibratory feeders or conveyors, without the spring system slipping in the
spring clamp elements 60.
The dashed lines on the right side of FIG. 7 indicate the displacement of
the chassis 24 and the deflection of the spring 26 as the armature 40 is
being attracted to the core of the electromagnet 38 when electric power is
applied to the magnetic coil 48. The dashed lines on the left side of FIG.
7 indicate the displacement of the chassis and the deflection of the
spring 26 after the armature 40 is released by the electromagnet 38 and
has moved by spring force. The arrows 140 indicate the direction of the
displacement of the armature 40 and the trough chassis 24 during
operation. The arrows 144 indicate the direction of the displacement of
the spring and clamping flexure member 54 as the spring 26 is deflected in
the characteristic "S" shaped form, as indicated by the dashed lines.
In the illustrated embodiment, the conveying apparatus is powered by an
electromagnet. It is not intended to limit the invention to single mass or
two mass electromagnetic feeders as it will be readily understood by those
skilled in the art that the invention would be useful over a broad range
of vibratory feeders and conveyor designs employing leaf springs. Any
drive means that can cause the trough 20 to reciprocate back and forth in
the direction of the arrows 140, such as rotating eccentric weights,
rotating crank arms, and the like, may also be employed and are
encompassed by the invention, regardless of any geometry differences and
in the placement or arrangement of the component parts. The geometry of
the flexure members 54 might also be varied to suit individual feeder or
conveyor designs without departing from the principles of the invention.
FIG. 8 illustrates the principles of the invention schematically. A first
structure 200, such as a trough, is connected at a connection 204 to a
leaf spring 208. The connection 204 is preferably a stack of spring bars.
The spring is connected at a connection 212 to a flexure member 216. The
connection is preferably a clamped connection. The flexure member 216 is
preferably a bar member. The flexure member 216 is connected at a
connection 220 to a second structure 226 such as a base. The connection
220 can be a bolted connection. The length of the spring 208 is preferably
arranged at about 90.degree. to the longitudinal axis of the flexure
member 216, although the invention is not limited to that angle as other
angles would be operational and are encompassed by the invention. The
apparatus shown in FIG. 8 could be turned upside down with the second
structure 226 being the trough and the first structure 200 being the base.
The first structure 200 and the second structure 226 are reciprocated
relative to each other along the direction W.
From the foregoing, it will be observed that numerous variations and
modifications may be effected without departing from the spirit and scope
of the invention. It is to be understood that no limitation with respect
to the specific apparatus illustrated herein is intended or should be
inferred. It is, of course, intended to cover by the appended claims all
such modifications as fall within the scope of the claims.
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